美国SR71黑鸟Word文档格式.docx

美国SR71黑鸟Word文档格式.docx

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Johnsonwasresponsibleformanyofthedesign'

sinnovativeconcepts.Duringaerialreconnaissancemissions,theSR-71operatedathighspeedsandaltitudestoallowittooutracethreats.Ifasurface-to-airmissilelaunchwasdetected,thestandardevasiveactionwassimplytoaccelerateandoutflythemissile.TheSR-71wasdesignedtohavebasicstealthcharacteristicsandservedasaprecursortofuturestealthaircraft.TheSR-71servedwiththeU.S.AirForcefrom1964to1998.Atotalof32aircraftwerebuilt;

12werelostinaccidentsandnonelosttoenemyaction.TheSR-71hasbeengivenseveralnicknames,includingBlackbirdandHabu.Since1976,ithasheldtheworldrecordforthefastestair-breathingmannedaircraft,arecordpreviouslyheldbytherelatedYF-12.

Design

Overview

TheSR-71wasdesignedforflightatoverMach3withaflightcrewoftwointandemcockpits,withthepilotintheforwardcockpitandtheReconnaissanceSystemsOfficer（RSO）monitoringthesurveillancesystemsandequipmentfromtherearcockpit.TheSR-71wasdesignedtominimizeitsradarcross-section,anearlyattemptatstealthdesign.Finishedaircraftwerepaintedadarkblue,almostblack,toincreasetheemissionofinternalheatandtoactascamouflageagainstthenightsky.Thedarkcolorledtotheaircraft'

scallsign"

.

WhiletheSR-71carriedradarcountermeasurestoevadeinterceptionefforts,itsgreatestprotectionwasitshighspeedandcruisingaltitudethatmadeitalmostinvulnerabletotheweaponsofitsday.Merelyacceleratingwouldtypicallybeenoughtoevadeasurface-to-airmissile,andtheplanewasfasterthantheSovietUnion'

sprincipalinterceptor,theMikoyan-GurevichMiG-25.TheMiG-25'

ssuccessor,theMiG-31,wasabletointercepttheSR-71,asitwascapableofMach2.8andarmedwiththeMach4.5R-33missile.SR-71overflightsoftheUSSRceasedfollowingMiG-31interceptsinthemid-1980s.Nonetheless,duringitsservicelife,noSR-71wasshotdown.

Airframe,canopyandlandinggear

Onmostaircraft,useoftitaniumwaslimitedbythecostsinvolved;

itwasgenerallyusedonlyincomponentsexposedtothehighesttemperatures,suchasexhaustfairingsandtheleadingedgesofwings.OntheSR-71,titaniumwasusedfor85%ofthestructure,withmuchoftherestpolymercompositematerials.Tocontrolcosts,Lockheedusedamoreeasilyworkedtitaniumalloywhichsoftenedatalowertemperature.ThechallengesposedledLockheedtodevelopnewfabricationmethods,andhavesincebeenusedinthemanufactureofotheraircraft.Weldingtitaniumrequiresdistilledwater,asthechlorinepresentintapwateriscorrosive;

cadmium-platedtoolscouldnotbeusedastheyalsocausedcorrosion.Metallurgicalcontaminationwasanotherproblem;

atonepoint80%ofthedeliveredtitaniumformanufacturewasrejectedonthesegrounds.

Thehightemperaturesgeneratedinflightrequiredspecialdesignandoperatingtechniques.Majorportionsoftheskinoftheinboardwingswerecorrugated,notsmooth.Aerodynamicistsinitiallyopposedtheconcept,disparaginglyreferringtotheaircraftasaMach3variantofthe1920s-eraFordTrimotor,knownforitscorrugatedaluminumskin.Theheatwouldhavecausedasmoothskintosplitorcurl,whereasthecorrugatedskincouldexpandverticallyandhorizontallyandincreasedlongitudinalstrength.

Fuselagepanelsweremanufacturedtoonlylooselyfitontheground.Properalignmentwasachievedastheairframeheatedupandexpandedseveralinches.Becauseofthis,andthelackofafuelsealingsystemthatcouldhandletheairframe'

sexpansionatextremetemperatures,theaircraftleakedJP-7fuelonthegroundpriortotakeoff.

Theouterwindscreenofthecockpitwasmadeofquartzandwasfusedultrasonicallytothetitaniumframe.Thetemperatureoftheexteriorofthewindscreenreached600°

F（316°

C）duringamission.

Coolingwascarriedoutbycyclingfuelbehindthetitaniumsurfacesinthechines.Onlanding,thecanopytemperaturewasover300°

C（572°

F）.TheredstripesonsomeSR-71sweretopreventmaintenanceworkersfromdamagingtheskin.Nearthecenterofthefuselage,thecurvedskinwasthinanddelicate,withnosupportfromthestructuralribs,whichwerespacedseveralfeetapart.

TheBlackbird'

stires,manufacturedbyB.F.Goodrich,containedaluminumandwerefilledwithnitrogen.Theycost$2,300anddidnotlast20missions.TheBlackbirdlandedatover170knotsanddeployedadragparachutetostop;

thechutealsoactedtoreducestressonthetires.

Shapeandthreatavoidance

Thefirstoperationalaircraftdesignedaroundastealthaircraftshapeandmaterials,theSR-71hadseveralfeaturesdesignedtoreduceitsradarsignature.TheSR-71hadaradarcross-section（RCS）ofaround10squaremeters.Drawingonearlystudiesinradarstealthtechnology,whichindicatedthatashapewithflattened,taperingsideswouldreflectmostenergyawayfromaradarbeam'

splaceoforigin,engineersaddedchinesandcantedtheverticalcontrolsurfacesinward.Specialradar-absorbingmaterialswereincorporatedintosawtooth-shapedsectionsoftheaircraft'

sskin.Cesium-basedfueladditiveswereusedtosomewhatreduceexhaustplumesvisibilitytoradar,althoughexhauststreamsremainedquiteapparent.KellyJohnsonlaterconcededthatSovietradartechnologyadvancedfasterthanthestealthtechnologyemployedagainstit.

TheSR-71featuredchines,apairofsharpedgesleadingaftfromeithersideofthenosealongthefuselage.ThesewerenotafeatureontheearlyA-3design;

Dr.FrankRodgersoftheScientificEngineeringInstitute,aCIAfrontorganization,discoveredthatacross-sectionofaspherehadagreatlyreducedradarreflection,andadaptedacylindrical-shapedfuselagebystretchingoutthesidesofthefuselage.AftertheadvisorypanelprovisionallyselectedConvair'

sFISHdesignovertheA-3onthebasisofRCS,LockheedadoptedchinesforitsA-4throughA-6designs.

Aerodynamicistsdiscoveredthatthechinesgeneratedpowerfulvorticesandcreatedadditionallift,leadingtounexpectedaerodynamicperformanceimprovements.Theangleofincidenceofthedeltawingscouldbereducedforgreaterstabilityandlessdragathighspeeds,andmoreweightcarried,suchasfuel.Landingspeedswerealsoreduced,asthechines'

vorticescreatedturbulentflowoverthewingsathighanglesofattack,makingithardertostall.Thechinesalsoactedlikeleading-edgeextensions,whichincreasetheagilityoffighterssuchastheF-5,F-16,F/A-18,MiG-29andSu-27.Theadditionofchinesalsoenabledtheremovaloftheplannedcanardforeplanes.

Airinlets

TheairinletsallowedtheSR-71tocruiseatoverMach3.2whilekeepingairflowintotheenginesattheinitialsubsonicspeeds.Mach3.2wasthedesignpointfortheaircraft,itsmostefficientspeed.Atthefrontofeachinlet,apointed,movableconecalleda"

spike"

（Inletcone）waslockedinitsfullforwardpositiononthegroundandduringsubsonicflight.WhentheaircraftacceleratedpastMach1.6,aninternaljackscrewmovedthespikeupto26inches（66cm）inwards,directedbyananalogairinletcomputerthattookintoaccountpitot-staticsystem,pitch,roll,yaw,andangleofattack.Movingthespiketipdrewtheshockwaveridingonitclosertotheinletcowlinguntilittouchedjustslightlyinsidethecowlinglip.Thispositionreflectedthespikeshock-waverepeatedlybetweenthespikecenterbodyandtheinletinnercowlsides,andminimizedairflowspillagewhichisthecauseofspillagedrag.Theairslowedsupersonicallywithafinalplaneshockwaveatentrytothesubsonicdiffuser.

Downstreamofthisnormalshocktheairissubsonic.Itdeceleratesfurtherinthedivergentducttogivetherequiredspeedatentrytothecompressor.Captureoftheplaneshockwavewithintheinletiscalled"

StartingtheInlet"

.Bleedtubesandbypassdoorsweredesignedintotheinletandenginenacellestohandlesomeofthispressureandtopositionthefinalshocktoallowtheinlettoremain"

started"

.TheSR-71wassometimesmoreefficientatspeedshigherthanMach3.2intermsofpoundsoffuelburnedpernauticalmiletraveled,dependingonoutsideairtemperature.Duringonemission,SR-71pilotBrianShulflewfasterthanusualtoavoidmultipleinterceptionattempts;

afterwards,itwasdiscoveredthatthishadreducedfuelconsumption.

Intheearlyyearsofoperation,theanalogcomputerswouldnotalwayskeepupwithrapidlychangingflightenvironmentalinputs.Ifinternalpressuresbecametoogreatandthespikewasincorrectlypositioned,theshockwavewouldsuddenlyblowoutthefrontoftheinlet,calledan"

InletUnstart"

.Duringunstartsafterburnerextinctionswerecommon.Theremainingengine'

sasymmetricalthrustwouldcausetheaircrafttoyawviolentlytooneside.SAS,autopilot,andmanualcontrolinputswouldfighttheyawing,butoftentheextremeoff-anglewouldreduceairflowintheoppositeengineandstimulate"

sympatheticstalls"

.Thisgeneratedarapidcounter-yawing,oftencoupledwithloud"

banging"

noises,andaroughrideduringwhichcrews'

helmetswouldsometimesstriketheircockpitcanopies.Oneresponsetoasingleunstartwasunstartingbothinletstopreventyawing,thenrestartingthemboth.Lockheedlaterinstalledanelectroniccontroltodetectunstartconditionsandperformthisresetactionwithout